Flame retardant composition for flammable plastic materials comprising 2,4,6-tris(2,4,6-tribromophenoxy)-1,3,5-triazine and process for producing the same

ABSTRACT

A flame retardant composition for flammable plastic materials and a method for producing the same are disclosed. The flame retardant composition comprises 2,4,6-tris(2,4,6-tribromophenoxy)-1,3,5-triazine that contains 1 to 1000 ppm of a metal species of a water-insoluble polyvalent metal compound selected from the group consisting of oxide, hydroxide, carbonate, phosphate, sulfate and silicate present in the particles of 2,4,6-tris(2,4,6-tribromophenoxy)-1,3,5-triazine. The flame retardant composition is produced by reacting an alkali metal salt of 2,4,6-tribromophenol and cyanuric chloride in the presence of said water-insoluble polyvalent metal compound.

TECHNICAL FIELD

The present invention relates to a flame retardant composition forflammable plastic materials comprising2,4,6-tris(2,4,6-tribromophenoxy)-1,3,5-triazine. It also relates to aprocess for producing said flame retardant composition.

BACKGROUND ART

2,4,6-Tris(2,4,6-tribromophenoxy)-1,3,5-triazine has been used as aflame retardant for plastic products. This compound may be synthesizedby reacting cyanuric chloride with an alkali metal phenolate, typicallysodium phenolate. During the reaction, an alkali metal halide, typicallysodium chloride is formed as a by-product and thus the resulting productmay be contaminated with a halide ion source. The product contaminatedwith the halide-ion source may result in various shortcomings when usedas a flame retardant for flammable plastic materials. When thermoplasticmaterials are rendered flame retarded it is conventional to blend thethermoplastic material and the flame retardant in molten state and themolten blend is molded into shaped articles. The halide ions from theirsource contained in the flame retardant may promote corrosion ofmetallic parts of extruders or other mixing apparatus as well as moldsand other metallic parts of shaping machines. The halide ions per se andrust pieces resulting from the corrosion of mixing or shaping machineparts may adversely affect the performance of shaped articles includingheat resistance, electrical properties and tracking resistance inparticular. Flame retardants are blended with thermosetting plasticmaterials for rendering them flame retarded. In this case, a dispersionor solution of solid flame retardant powder is added, for instance, to aresin varnish. Then prepregs are prepared from the varnish forfabricating a metal clad laminate for the production of a printedcircuit board. If the flame retardant contains a halide ion source atunacceptable level, the electrical properties of the board is greatlycompromised.

2,4,6-Tris(2,4,6-tribromophenoxy)-1,3,5-triazine (hereinafter simplycalled “brominated phenoxytriazine”) was first described in FrenchPatent No. 1,566,675 wherein the compound is synthesized by adding asuspension of cyanuric chloride in acetone to a solution of sodium2,4,6-tribromophenolate in benzene/acetone mixture.

U.S. Pat. No. 3,843,650 discloses the synthesis of brominatedphenoxytriazine by the addition of cyanuric chloride to an ethanolicsolution of sodium tribomophenolate. U.S. Pat. No. 5,965,731 disclosesthe synthesis of brominated phenoxytriazine by successively adding anaqueous solution of sodium hydroxide and a solution of cyanuric chloridein acetone to a solution of tribormophenol in acetone.

U.S. Pat. No. 4,039,538 discloses a reaction of an alkali metaltribromophenolate dissolved in an alkylene glycol monoalkyl ether suchas methyl- or ethylcellosolve with cyanuric chloride.

JP 7/25859A, JP 7/25860A and JP 7/25861A disclose a reaction between aconcentrated aqueous tribromophenolate solution/methylene chloridemixture and a solution or suspension of cyanuric chloride in methylenechloride in the presence of a tertiary amine and/or phase transfercatalyst.

Whichever process is employed, the concentration of alkali metal halidesuch as NaCl or KCl in the reaction system increases as the reactionproceeds. At the same time, brominated phenoxytriazine formed willcrystallize out because its solubility in water and organic solvents isvery low. Therefore, it is inevitable to entrain the halide salt bybrominated phenoxytriazine when crystallizing from the reaction mixture.In order to minimize the entrainment of the halide salt, it would beeffective to maintain the concentration of the halide salt in thereaction system as low as possible by decreasing the amounts of chargedalkali metal phenolate and cyanuric chloride per unit volume of thereaction medium. This approach naturally decreases the amount of thetarget product to be recovered as crystals and is, therefore, hardlyapplicable to an industrial scale production due to low productivity.

Once contained in the crystals, it is difficult to remove the halidesalt from brominated phenoxytriazine by washing with a solvent of thehalide salt such as water, ethanol or acetone. Accordingly, one of otherconceivable approaches to reduce the halide salt content would bedissolving the crystals containing the halide salt in a large volume ofan organic solvent in which the crystals are soluble and recrystallingthe product from the solution, or reverse extracting the halide saltfrom the above solution and then evaporating the organic solvent. It isalso conceivable to repeat the washing of finely divided crystalscontaining the halide salt with water or ethanol. However, all of theseapproaches are hardly applicable to an industrial scale production dueto low productivity.

Accordingly, a need exists for a flame retardant composition comprising2,4,6-tris(2,4,6-tribromophenoxy)-1,3,5-triazine which has a minimumcontent of halide salts and other deteriorative impurities. Also, a needexists for a process for producing said flame retardant composition.

SUMMARY OF INVENTION

According to the present invention, there is provided a flame retardantcomposition for flammable plastic materials comprising particulate2,4,6-tris(tribrophenoxy)-1,3,5-triazine containing 1 to 1000 ppm of ametal species of a water-insoluble polyvalent metal compound selectedfrom the group consisting of oxide, hydroxide, carbonate, phosphate,sulfate and silicate, said water-insoluble polyvalent metal compoundbeing present in said particulate2,4,6-tris(2,4,6-tribromophenoxy)-1,3,5-triazine in a physicallyindiscrete form.

The present invention also provides a process for producing said flameretardant composition comprising reacting an alkali metaltribromophenolate and cyanuric chloride in the presence of 0.01 to 10%by weight of cyanuric chloride of finely divided particles of awater-insoluble polyvalent metal compound selected from the groupconsisting of oxide, hydroxide, carbonate, phosphate, sulfate andsilicate.

Although the invention is not bound to any particular theory, it ispostulated that the finely divided water-insoluble polyvalent metalcompound present in the reaction system serves as a nucleus for growingcrystals, and promote, as the reaction proceeds, crystallization ofbrominated tribromophenoxytriazine without entraining the halide salt inthe crystals. Instead, the product produced according to presentinvention contains more than 1 ppm of a metal species corresponding tothe polyvalent metal compound employed. The presence thereof, however,does not have any adverse effect on the flame retarded plastic articlesand shaping machines therefor.

In another aspect, the present invention provides said flame retardantcomposition having reduced content of halide ion sources produced by themethod of the present invention wherein the product contains 1 to 1000ppm of at least one metal species corresponding to said polyvalent metalcompound.

DESCRIPTION OF EMBODIMENTS

Except the reaction is carried out in the presence of saidwater-insoluble polyvalent metal compound, the process of the presentinvention may be otherwise identical to those known in the art includingthe processes disclosed in the patents cited above.

The process of the present invention may be carried out by adding saidinsoluble multivalent metal compound to any of reaction systemsaccording to the above known processes. The insoluble metal salt whichmay be employed in the present invention includes oxide, hydroxides,carbonates, phosphates, sulfates or silicates of a polyvalent metal suchas magnesium, calcium, barium, aluminum, silicon, titanium, zirconium orantimony. Examples thereof include magnesium hydroxide, magnesiumcarbonate, magnesium phosphate, magnesium sulfate, magnesium silicate,calcium hydroxide, calcium carbonate, calcium phosphate, calciumsulfate, calcium silicate, barium carbonate, barium phosphate, bariumsulfate, aluminum oxide, aluminum carbonate, aluminum phosphate,aluminum silicate, silicon oxide (silica), titanium dioxide, zirconiumdioxide and antimony trioxide. Naturally occurring or synthetic mineralscomprising a polyvalent metal silicate complex such as talc, bentonite,kaolin or zeolite may also be used. Calcium carbonate, silica, bariumsulfate, talc, aluminum polyphosphate, zirconium dioxide, titaniumdioxide, antimony trioxide and calcium silicate are particularlypreferred because they serve to prevent coloring and decomposition of aplastic material when blending with the flame retardant composition atan elevated temperature.

The term “water-insoluble polyvalent metal compound” as used hereinrefers to the compound having a solubility in water of less than 1 g/L,preferably less than 0.5 g/L at 25° C. As stated before, the finelydivided insoluble polyvalent compound appear to serve as a nucleus ofcrystallization. For this reason, it is advantageous for the finelydivided particles to have a large number of discrete particles per unitweight to minimize the amount of the metal compound to be added.Preferably, the particles have a mean diameter of less than 10 microns,more preferably less than 5 microns. Of particularly preferablyparticles are fumed silica having a mean diameter of nanometer order.

The amount of addition of the finely divided polyvalent metal compoundgenerally ranges from 0.01 to 10% by weight of cyanuric chloride but itmay vary depending upon the number of particles per unit weight, namelythe mean diameter thereof. The smaller in the mean diameter, the feweramount of addition.

The finely divided particles of the polyvalent metal compound are neededto exist in the reaction system before the crystallization of thereaction product takes place. Typically the finely divided particles areinitially added to either one of the reactants, for example, to asolution of phenolate. The cyanuric chloride reactant may subsequentlybe added to the phenolate solution. Alternatively, the finely dividedparticles may be added to a solution of phenolate together with thecyanuric chloride reactant. Instead of pre-formed finely dividedparticles, it is possible to form the finely divided particles in situin the reaction system as a slurry. For example, calcium carbonate maybe formed in the reaction system by the reaction of calcium chloride andsodium carbonate. Similarly calcium phosphate may be formed by thereaction of calcium chloride and sodium phosphate.

The reaction may be carried out at a temperature from room temperatureto the boiling point of the reaction medium. However, it is preferableto continue the reaction to completion at reflux temperature of thereaction mixture after all reactants have been added to the reactionvessel. After the reaction, the precipitated reaction product isfiltered off, washed and dried. The filtration may be carried out usinga conventional filter device or a centrifuge and washing of theresulting filter cake may be carried out thereon using water or amixture of water and an organic solvent in which the alkali metal halideis soluble. The organic solvent is preferably a water-miscible solventincluding methanol, ethanol, isopropanol, ethylene glycol, glycerine,acetone, DMF, THF, dioxane and the like. The washing efficiency isenhanced by the use of a water-miscible organic solvent due to enhancedaffinity between the brominated phenoxytriazine and the solvent.However, it is preferable to use water alone in the final washing stepto eliminate emission of VOC to the atmosphere upon drying the endproduct.

According to the present invention, the amount of halide ion sourcecontaminants is reduced to less than 500 ppm calculated as NaCl. Thisamount may be reduced further to less than 250 ppm by suitably selectingparticular kind of insoluble polyvalent metal compounds and theirparticle size. Instead, the product contains the finely dividedpolyvalent metal compound from 1 ppm to 1000 ppm calculated as the metalspecies corresponding to said water-insoluble metal compound. Such asmall amount of the water-insoluble metal compound has no or littleeffect on the performance of the reaction product and shaped plasticarticles containing the same. Namely, the flame retardant compositionneither deteriorates the heat stability of shaped plastic articles norpromotes corrosion of mixing and shaping machines.

The amount of halide ions entrained into the reaction product may bedetermined by the potentiometric titration with AgNO₃ as outlined below,while the amount of metal species of the water-insoluble metal compoundmay be determined by the atomic absorption spectrometry or theinductively coupled plasma method.

In addition to the halide salt produced as a by-product, otherelectrolytes such as unreacted alkali metal phenolate may be present inthe reaction system. They may also be entrained into the resultingbrominated phenoxytriazine crystals. These electrolyte impurities alsohave an adverse effect on the electrical properties of the plasticarticles containing the contaminated reaction product. These otherelectrolytic impurities are incapable of detecting by the potentiometrictitration with AgNO₃ but capable of detecting quantitatively by leachingthe crystals with water and measuring the electroconductivity of watercontaining the electrolytic impurities. According to the presentinvention, it is possible to reduce the halide ion level as determinedby the potentiometric titration with AgNO₃ to less than 500 ppmcalculated as NaCl and at the same time, to decrease the total level ofelectrolytes including the halide salt represented by theelectroconductivity of leaching water to an acceptable level of lessthan 50×10⁻⁶ S/cm.

Contrary to the present invention, the corresponding reaction productsproduced by similar processes in the absence of the finely dividedwater-insoluble metal compound showed to contain at least 1000 ppm ofthe halide ion sources and an electroconductivity level of leachingwater higher than 150×10⁻⁶ S/cm. These halide ion levels and theelectroconductivity levels could not be decreased to an acceptable levelby washing the crystals as produced or pulverized crystals withmethanol.

EXAMPLES

The invention will now be illustrated by the following examples. Allparts and percents therein are by weight unless otherwise indicated.

Part I. Production of brominated phenoxytriazine

Materials

(1) Cyanuric chloride: industrial grade F available from Deggussa, 99.7%purity, metal content <10 ppm.(2) Calcium carbonate: Nanox #30, available from Maruo Calcium Co.,Ltd., mean diameter about 1 micron.(3) Titanium dioxide; PF711 available from Ishihara Sangyo Kaisha, meandiameter about 0.25 microns.(4) Fumed silica; Aerosil 200 available from Japan Aerosil, meandiameter 12 nm.(5) Precipitated barium sulfate; available from Toshin Kasei Co., Ltd.,mean diameter 0.5 microns.(6) Talc (magnesium silicate); Microace P-3 available from Nippon TalcCo. Ltd., mean diameter 5 microns.(7) Aluminum polyphosphate (AlH₂P₃O₁₀-2H₂O); K-White #85 available fromTayca Corporation, mean diameter 3.7 microns.(8) Zirconium dioxide; EP grade available from Daiichi Rare ElementsChemical Industry Co., Ltd., mean diameter 2.2 microns.(9) Antimony trioxide; AN-800(T) available from Dai-ichi Kogyo SeiyakuCo., Ltd., means diameter 1.1 microns.

Test Method (1) Quantitative Analysis of Metals in Samples

The inductively coupled plasma method was used by dissolving the samplein DMF. First, a standard curve was generated using specimens havingknown contents of the metal. Then the metal content of a test samplehaving unknown metal content was determined by the intrapolation method.An IPC analyzer CIROS-120 available Rigaku was used.

(2) Determination of NaCl Content

5.0 g of the sample was precisely weighed in a 100 ml beaker anddissolved in 50 ml of dioxane completely. To the solution was added 5 mlof deionized water with stirring. Then the halide ion concentration ofthe resulting solution was determined by the potentiometric titrationwith 0.01 mol/L AgNO₃ under acidic conditions with nitric acid. Themeasured halide ion concentration was converted to the content of NaClin the sample in terms of weight %. If the halide salt content in thesample is too high, the weight of sample is decreased such that theendpoint is reached with 1-5 ml of 0.01 mol/L AgNO₃.

(3) Electroconductivity of Leaching Water

5.0 g of the sample was weighed in a 100 ml polypropylene container anddissolved in 30 ml of dioxane completely. To the solution was added 50ml of deionized water portionwise with stirring to precipitate a portionof brominated phenoxytriazine dissolved in dioxane. Theelectroconductivity of the resulting aqueous slurry was measured at24.5-25.5° C. using an electroconductivity meter CM-30S and an electrodeCGT-511B (cell constant=0.966/cm) both available from Toa Dempa KogyoCo. Ltd. All containers, instruments and liquids (dioxane, water) wereused after verifying to have an electroconductivity of less than 1×10⁻⁶S/cm in the blank test.

Example 1

To a 500 ml flask equipped with a stirrer, a thermometer and a refluxcondenser were charged with 370 ml of methylcellosolve, 7.2 g (0.18 mol)of flaky sodium hydroxide, 59.15 g (0.18 mol) of tribromophenol, and0.10 g of calcium carbonate (9% of cyanuric chloride). The mixture washeated to 60° C. and 11.1 g (0.06 mol) of cyanuric chloride was addedportionwise to the mixture over 3 minutes with stirring whereupon theinner temperature elevated to 70° C. As the reaction proceeds, themixture became a slurry. Then the mixture was heated to 110° C. and thereaction was continued at this temperature to completion. The reactionmixture was allowed to cool to room temperature and filtered on aBuchner funnel. The filter cake was washed first with 100 ml of methanoland then with 100 ml of water each at several times until the NaClcontent in the washing reached below 100 ppm. Three times washing withwater was needed until the NaCl content of the washing decreased belowthe above level. The wet filter cake was dried in an over at 130° C.until an equilibrium was reached to give 56.3 g (88%) of the desiredproduct. The product showed to have a NaCl content of 350 ppm and anelectroconductivity of leaching water of 40×10⁻⁶ S/cm.

Example 2

To the same flask as used in Example 1 were charged with 100 ml ofacetone, 99.2 g (0.3 mol) of tribromophenol, 50 g of 25% aqueoussolution of sodium hydroxide (0.31 mol as NaOH), and 0.2 g of titaniumdioxide (1.1% of cyanuric chloride). The mixture was heated to reflux.Then a solution of 18.4 g (0.1 mol) of cyanuric chloride in 100 ml ofacetone was added dropwise to the mixture over 30 minutes, and thereaction mixture in the form of slurry was allowed to react at refluxtemperature for additional 3 hours. After cooling to room temperature,the reaction mixture was filtered and the filter cake was washed firstwith 100 ml of acetone and then with 100 ml of water each at severaltimes until the NaCl content in the washing decreased below 100 ppm.Three times washing with water was needed until the above NaCl level wasreached. The wet filter cake was dried in an oven at 130° C. until anequilibrium was reached to give 102 g (96%) of the desired product. Theproduct showed to have a NaCl content of 140 ppm and anelectroconductivity of leaching water of 18×10⁻⁶ S/cm.

Example 3

To the same flask as used in Example 1 were charged with 150 g of water,17.1 g (0.43 mol) of flaky sodium hydroxide, 0.07 g of sodium sulfite,and 12.5 mg (0.05% of cyanuric chloride) of fumed silica. The mixturewas stirred to obtain a homogeneous solution and then cooled to 10° C.To this was added 136 g (0.136 mol) of tribromophenol. Separately, 25.0g (0.136 mol) of cyanuric chloride was dissolved in 160 g of methylenechloride and 1.0 g of 30% aqueous solution of trimethylamine was addedthereto. The cyanuric chloride solution thus prepared was added dropwiseto the tribromophenol solution in the flask at a temperature of 3-30° C.After the addition the reaction mixture was heated to reflux temperaturefor 30 minutes to complete the reaction. Then methylene chloride wasdistilled off under atmospheric pressure. The residue was allowed tocool to room temperature and the resulting precipitate was filtered offand washed with 100 ml of water each at several times until the NaClcontent in the washing decreased below 100 ppm. Three times washing wasneeded until the above NaCl level was reached. The washed filter cakewas dried in an oven at 130° C. until an equilibrium was reached to give284.3 g (98%) of the desired product. The product showed to have a NaClcontent of 220 ppm and an electroconductivity of leaching water of20×10⁻⁶ S/cm.

Example 4

To the same flask as used in Example 1 were charged with 96 g of water,34.2 g (0.86 mol) of flaky sodium hydroxide and 0.14 g of sodium sulfitewhile stirring. The resulting solution was cooled to 10° C. To thesolution were added 130 g of methylene chloride and 272 g (0.82 mol) oftribromophenol. Then 50.0 g (0.27 mol) of cyanuric chloride and 75 mg offumed silica (0.3% of cyanuric chloride) were gradually added to thesolution at a temperature of 3-30° C. After the addition, the reactionmixture was heated to reflux temperature for additional 30 minutes tocomplete the reaction, and then methylene chloride was distilled offunder atmospheric pressure. The residue was allowed to cool to roomtemperature and the resulting precipitate was filtered off. The filtercake was repeatedly washed with 100 ml of water each time until the NaClcontent in the washing reached below 100 ppm. Three times washing wasneeded to decrease the NaCl level below 100 ppm. The washed filter cakewas dried in an oven at 130° C. until an equilibrium was reached to give284.3 g (98%) of the desired product. The product showed to have a NaClcontent of 90 ppm and an electroconductivity of leaching water of15×10⁻⁶ S/cm.

Example 5

The procedure of Example 3 was repeated except that 50 mg ofprecipitated barium sulfate (0.2% of cyanuric chloride) was added to thereaction system in place of 12.5 mg of fumed silica. Three times washingwith water was needed to decrease the NaCl concentration in the washingbelow 100 ppm. The washed filter cake was dried in an oven at 130° C.until an equilibrium was reached to give 142.2 g (98%) of the desiredproduct. The product showed to have a NaCl content of 110 ppm and anelectroconductivity of leaching water of 20×10⁻⁶ S/cm.

Example 6

The procedure of Example 3 was repeated except that 0.25 g of talc (1.0%of cyanuric chloride) was added to the reaction system in place of 12.5mg of fumed silica. Three times washing with water was needed todecrease the NaCl concentration in the washing below 100 ppm. The washedfilter cake was dried in an oven at 130° C. until an equilibrium wasreached to give 142.3 g (98%) of the desired product. The product showedto have a NaCl content of 70 ppm and an electroconductivity of leachingwater of 12×10⁻⁶ S/cm.

Example 7

The procedure of Example 4 was repeated except that 0.5 g of aluminumpolyphosphate was added to the reaction system in place of 75 mg offumed silica. Three times washing with water was needed to decrease theNaCl concentration in the washing below 100 ppm. The washed filter cakewas dried in an oven at 130° C. until an equilibrium was reached to give285.0 g (98%) of the desired product. The product showed to have a NaClcontent of 180 ppm and an electroconductivity of leaching water of22×10⁻⁶ S/cm.

Example 8

The procedure of Example 4 was repeated except that 0.5 g of zirconiumdioxide (1.0% of cyanuric chloride) was added to the reaction system inplace of 75 mg of fumed silica. Three times washing with water wasneeded to decrease the NaCl concentration in the washing below 100 ppm.The washed filter cake was dried in an oven at 130° C. until anequilibrium was reached to give 283.5 g (98%) of the desired product.The product showed to have a NaCl content of 100 ppm and anelectroconductivity of leaching water of 17×10⁻⁶ S/cm.

Example 9

To the same flask as used in Example 1 were charged with 150 g of water,17.1 g (0.43 mol) of flaky sodium hydroxide, 0.07 g of sodium sulfite,and 0.4 g of calcium chloride. Then 4.0 g of 10% phosphoric acid wasgradually added to the mixture with stirring whereupon a milky solutionin which fine particles of water-insoluble calcium phosphate aresuspending was obtained. The mean particle diameter of calcium phosphatewas measured as about 3 microns and the total weight of the suspendedcalcium phosphate particles was calculated as about 0.5 g (about 2% ofcyanuric chloride) from the amounts of starting reactants. The milkysolution was cooled to 10° C. and 136 g (0.136 mol) of tribromophenolwas dissolved in this solution. Using the resulting tribromophenolsolution, the reaction with cyanuric chloride was carried out as inExample 3. Three times washing with water was needed to decrease theNaCl concentration in the washing below 100 ppm. The washed filter cakewas dried in an oven at 130° C. until an equilibrium was reached to give142 g (98%) of the desired product. The product showed to have a NaClcontent of 230 ppm and an electroconductivity of leaching water of36×10⁻⁶ S/cm.

Example 10

To the same flask as used in Example 1 were charged with 150 g of water,17.1 g (0.43 mol) of flaky sodium hydroxide, 0.07 g of sodium sulfite,and 0.75 g (3.0% of cyanuric chloride) of antimony trioxide. The mixturewas stirred to obtain a homogeneous solution and then cooled to 10° C.To this was added 136 g (0.136 mol) of tribromophenol. Separately, 25.0g (0.136 mol) of cyanuric chloride was dissolved in 160 g of methylenechloride and 1.0 g of 30% aqueous solution of trimethylamine was addedthereto. The cyanuric chloride solution thus prepared was added dropwiseto the tribromophenol solution in the flask at a temperature of 3-30° C.After the addition the reaction mixture was heated to reflux temperaturefor 30 minutes to complete the reaction. Then methylene chloride wasdistilled off under atmospheric pressure. The residue was allowed tocool to room temperature and the resulting precipitate was filtered offand washed with 100 ml of water each at several times until the NaClcontent in the washing decreased below 100 ppm. Three times washing wasneeded until the above NaCl level was reached. The washed filter cakewas dried in an oven at 130° C. until an equilibrium was reached to give285.0 g (98%) of the desired product. The product showed to have a NaClcontent of 84 ppm and an electroconductivity of leaching water of16×10⁻⁶ S/cm.

Comparative Example 1

Example 1 was repeated in the absence of calcium carbonate. The productshowed to have a NaCl content of 2,300 ppm and an electroconductivity ofleaching water of 180×10⁻⁶ S/cm.

Comparative Example 2

Example 2 was repeated in the absence of titanium dioxide. The productshowed to have a NaCl content of 4,600 ppm and an electroconductivity ofleaching water of above 200×10⁻⁶ S/cm.

Comparative Example 3

Example 3 was repeated in the absence of fumed silica. The productshowed to have a NaCl content of 7,300 ppm and an electroconductivity ofleaching water of above 200×10⁻⁶ S/cm.

Comparative Example 4

Example 4 was repeated in the absence of fumed silica. The productshowed to have a NaCl content of 11,500 ppm and an electroconductivityof leaching water of above 200×10⁻⁶ S/cm.

Comparative Example 5

To the same flask as used in Example 1 were charged with 100 g of theproduct of Comparative Example 4 having a mean diameter of 100 micronsand 300 ml of methanol. The mixture was stirred at reflux temperaturefor 1 hour and then allowed to cool to room temperature. Solids wererecovered from the mixture by filtration, washed with 2×100 ml of water,and dried in an oven at 130° C. until an equilibrium was reached. TheNaCl content of the product decreased to 8,900 ppm by the abovetreatment but the electroconductivity of leaching water remained above200×10⁻⁶ S/cm.

Comparative Example 6

The procedure of Comparative Example 5 was repeated after pulverizingthe product of Comparative Example 4 from 100 microns mean diameter to 5microns mean diameter. The NaCl content decreased to 970 ppm while theelectroconductivity of leaching water decreased to 85×10⁻⁶ S/cm by theabove treatment.

Part II. Evaluation of brominated phenoxytriazine

Materials

1) Brominated phenoxytriazine;

Products of Examples 1-4 and Comparative Examples 1-6 were used.

2) Fiber glass reinforced polybutylene terephthalate;

Novaduran 5010G30 available from Mitsubishi Engineering Plastics.

3) Antimony trioxide;

Pyroguard AN-800(T) available from Dai-Ichi Kogyo Seiyaku Co., Ltd.

4) Antioxidant;

Irganox 245 available Ciba Specialty Chemicals.

Preparation of Test Pieces

Meterial Parts Fiber glass reinforced polybutylene 100.0 terephthalateBrominated phenoxytriazine 12.0 Antimony trioxide 4.0 Antioxidant 0.2

The mixture of the above formulation was kneaded in a twin screwextruder having an inner diameter of 20 mm at 250° C. and extrudedthrough a die. The extrudate was cooled and cut into pellets. Afterdrying at 80° C. under reduced pressure the pellets were injectionmolded into various test pieces for respective testing. The moldtemperature was 60° C. The test pieces were stored in a desiccator untilimmediately before use.

Test Method (1) Melt Mass Flow Rate (MFR)

Using the pellets before molding, MFR was determined according to JISK7210, method A at a temperature of 250° C. and a load of 2.116 kg.

(2) Flame Retardancy

The flame retardancy was evaluated by the vertical combustion methodaccording to UL-94 standard. The size of test piece was 127 mm inlength, 12.5 mm in width and 0.8 mm in thickness.

(3) Heat distortion temperature (HDT)

HDT was determined according to JIS K6810. The size of test piece was127 mm in length, 12.7 mm in height and 3.2 mm in width. The heatdistortion temperature refers to a temperature at which the test pieceis distorted through 0.254 mm under a load of 4.6 kgf/cm².

(4) Flexural Strength

The flexural strength was determined according to JIS K7203 using thesame test piece used for determining HTD. The test was carried out at adistance between supporting point of 68 mm and a bending rate of 2mm/min. The flexural strength was calculated from the maximum bendingload.

(5) Tracking resistance

The tracking resistance was determined according to JIS C2134. The testpiece was a square plate of 50×50×3.2 mm size having smooth surfaces.

(6) Tracking Resistance after Accelerated Aging

The same test piece as used in the method (5) was subjected 10 cycles ofplacing the test piece first at a temperature of 80° C. and at arelative humidity of 90% for 24 hours and then at a temperature of 25°C. and at a relative humidity of 20% for 24 hours. After the treatment,the test piece was dried at 80° C. under reduce pressure for 24 hoursand allowed to cool to room temperature in a desiccator. During theabove treatment, care was taken to leave the test surfaces untouched.After the above treatment, the tracking resistance was determined asabove.

(7) Heat Stability

The same test piece as used in the method (5) was used in this test. Thetest piece was hot pressed at 280° C. for 30 minutes. Color differencedeltaE of the heat treated test piece was determined by measuring thecolor before and after the heat treatment. The heat stability wasevaluated by the color difference deltaE according to the followingschedule.

Good: deltaE<5

Fair: deltaE=5-10

Not Good: deltaE>10

(8) Metal Mold Corrosiveness

2 g of the resin pellets for preparing the test pieces was placed on aclean surface of quenched SKD-11 steel plate and covered with invertedPetri dish. The steel plate with the resin pellets thereon was heated inan oven at 280° C. for 1 hour and then removed from the oven. Thesurface of the steel plate in the area covered by the Petri dish wasvisually inspected if rust or other indications of corrosion developed.

Results

The results of Part I and Part II are shown in tables 1-2 and Table 3respectively.

TABLE 1 EXAMPLE Item 1 2 3 4 5 Insoluble metal compound CaCo₃ TiO₂ SiO₂SiO2 BaSO₄ Amount(% of cyanuric 9.0 1.1 0.05 0.3 0.2 chloride) Yield (%)88 96 97 98 98 NaCl content(ppm) 350 140 220 90 110 Metal Species Ca TiSi Si Ba Metal content(ppm) 260 100 8 57 27 Conductivity of leaching 4018 20 15 20 water (×10⁻⁶ S/cm) EXAMPLE Item 6 7 8 9 10 Insoluble metalcompound Talc P3-A1¹⁾ ZrO₂ Ca—PO₄ ²⁾ Sb₂O₃ Amount(% of cyanuric 1.0 1.01.0 about 2.0 3.0 chloride) Yield (%) 98 98 98 98 98 NaCl content(ppm)70 180 100 230 84 Metal Species Mg Al Zr Ca Sb Metal content(ppm) 74 10630 15 315 Conductivity of leaching 12 22 17 36 16 water (×10⁻⁶ S/cm)¹⁾Aluminum polyphosphate; ²⁾Reaction product between CaCl₂ and H₃PO₄

TABLE 2 COMPARATIVE EXAMPLE Item 1 2 3 Insoluble metal compound Not NotNot present present present Yield (%) 86 95 97 NaCl content(ppm) 2,3004,600 7,300 Conductivity of leaching 180 >200 >200 water (×10⁻⁶ S/cm)COMPARATIVE EXAMPLE Item 4 5 6 Insoluble metal compound Not Not Notpresent present present Yield (%) 98 — — NaCl content(ppm) 11,500 8,900970 Conductivity of leaching >200 >200 85 water (×10⁻⁶ S/cm)

TABLE 3 Run No. Item 1 2 3 4 Brominated phenoxytriazine Ex. 1 Ex. 2 Ex.3 Ex. 4 MFR, g/10 min. 22 22 22 22 Flame retardancy (VL-94) V-0 V-0 V-0V-0 HDT, ° C. 200.5 200.5 200.5 200.5 Flexural strength, MPa 212 210 214214 Tracking resistance, V 420 430 430 430 Tracking resistance 410 430430 430 after aging, V Decrease in tracking 10 0 0 0 resistance, V Heatresistance Good Good Good Good Corrosiveness No No No No Run No. Item 56 7 Brominated phenoxytriazine Comp. Ex, 4 Comp. Ex. 5 Comp. Ex. 6 MFR,g/10 min. 22 22 22 Flame retardancy (VL-94) V-0 V-0 V-0 HDT, ° C. 200.5200.5 200.5 Flexural strength, MPa 208 210 212 Tracking resistance, V340 360 380 Tracking resistance 210 260 300 after aging, V Decrease intracking 130 100 80 resistance, V Heat resistance Not good Not good Notgood Corrosiveness Yes Yes Yes

As demonstrated by Examples 1-10, it is possible to drastically reducethe content of NaCl in the reaction product by adding an amount of awater-insoluble polyvalent metal compound to the reaction system. At thesame time, the electroconductivity of water used for leaching thereaction product, the parameter representing the content of watersoluble ionizable impurities, was reduced below 50×10⁻⁶ S/cm. Theproducts of Examples 1-10 contain a detectable level of a metal speciescorresponding to the water-insoluble metal compound added to thereaction system. The detection of a metal specie, in this case,demonstrates that the contents of NaCl and other ionizable impurities inthe crystalline product have been reduced to an acceptable level.

The products of Comparative Examples 1-4 showed to contain a largeamount of NaCl produced as by-product. Attempts have been made inComparative Example 5 to reduce the NaCl content by leaching the productwith methanol in which NaCl is soluble. However, the reduction of NaClcontent was only up to about 20%. In order to improve the leachingefficiency, the reaction product was pulverized before leaching inComparative Example 6. The content of NaCl was decreased to about onetenth. From the results of Comparative Examples 1-6, it is consideredthat several additional steps such as leaching and pulverizing steps areessential to reduce the NaCl content from the products of prior artprocesses. These additional steps are disadvantageous not only in termsof productivity but also economically.

The products of Examples and Comparative Examples show distinctivedifference in performance when used for producing flame retarded plasticarticles. The hue and mechanical strength properties are comparablebetween them but improvements may be seen in the products of Examples inthe durability of electroproperties, particularly after experiencinghigh/low temperature and humidity hysteresis. The product of Exampleshave been proven to have no corrosiveness against metallic molds.

1. A flame retardant composition for flammable plastic materialscomprising particulate 2,4,6-tris(2,4,6-tribromophenoxy)-1,3,5-triazinecontaining 1 to 1000 ppm of a metal species of a water-insolublepolyvalent metal compound selected from the group consisting of oxide,hydroxide, carbonate, phosphate, sulfate and silicate, saidwater-insoluble polyvalent metal compound being present in saidparticulate 2,4,6-tris(2,4,6-tribromophenoxy)-1,3,5-triazine in aphysically indiscrete form.
 2. The flame retardant composition accordingto claim 1 wherein the amount of said metal species is up to 500 ppm. 3.The flame retardant composition according to claim 1 wherein said metalspecies is magnesium, calcium, barium, aluminum, silicon, titanium,zirconium or antimony.
 4. The flame retardant composition according toclaim 1 wherein said water-insoluble polyvalent metal compound is talc,calcium carbonate, calcium phosphate, barium sulfate, aluminumpolyphosphate, silica, titanium dioxide, zirconium dioxide or antimonytrioxide.
 5. The flame retardant composition according to claim 1wherein the content of halide ion sources calculated as NaCl of thecomposition is less than 500 ppm when determined by the potentiometrictitration with AgNO₃.
 6. The flame retardant composition according toclaim 1 wherein the electroconductivity of leaching water of thecomposition is less than 50×10⁻⁶ S/cm.
 7. A process for producing aflame retardant composition for flammable plastic materials comprising2,4,6-tris(2,4,6-tribromophenoxy)-1,3,5-triazine, said processcomprising reacting an alkali metal salt of 2,4,6-tribromophenol andcyanuric chloride in the presence of 0.01 to 10% by weight of cyanuricchloride of finely divided particles of a water-insoluble polyvalentmetal compound.
 8. A process according to claim 7 wherein saidpolyvalent metal is magnesium, calcium, barium, aluminum, silicon,titanium, zirconium or antimony.
 9. A process according to claim 7wherein said water-insoluble polyvalent metal compound is calciumcarbonate, silica, barium sulfate, talc, aluminum polyphosphate,titanium dioxide, zirconium dioxide, antimony trioxide or calciumphosphate.
 10. A process according to claim 7 wherein saidwater-insoluble polyvalent metal compound has a mean particle diameterof less than 10 microns.
 11. A process according to claim 7 wherein saidfinely divided particles of the water-insoluble polyvalent metalcompound is present in a solution of said alkali metal salt oftribromophenol, and wherein said cyanuric chloride reactant is added tosaid solution.
 12. A process according to claim 7 wherein said finelydivided particles of the water-insoluble polyvalent metal compound andsaid cyanuric chloride reactant are simultaneously added to a solutionof said alkali metal salt of tribromophenol.
 13. A process according toclaim 7 further comprising the steps of filtering the reaction mixtureto recover the precipitated reaction product, and washing the recoveredreaction product with water and/or an organic solvent in which an alkalimetal halide is soluble.
 14. A process according to claim 13 furtherincluding the step of drying said reaction product after washing.